Roy,
Don't know about 'over there', but 'over here', the system has to look for a clear channel/frequency. That means that the TX and RCVR have to have a unique ID and only respond to that ID. Makes things a bit more complicated/expensive, but works nicely. 'Mistakes' do happen, but usually because 'things' aren't done 'right', which can also be a matter of design and not operator error.
- 'Doc